High resiliency polyurethane foams are produced by the reaction of organic osocyanates, water, and high molecular weight polyols which have greater than 40% of primary hydroxyl capping. They are distinguishable, in part, from conventional hot cure polyurethane foams by the use of such a high percentage of primary hydroxyl groups, as well as by the fact that they require little or no oven curing. Thus they are often referred to as cold cure foams. High resiliency polyurethane foams are extremely desirable for cushioning applications because of the excellent physical properties they offer such as high resiliency, open cell structure, low fatigue for long life, and high sag factors for good load bearing capabilities.
The ingredients for high resiliency polyurethane foam are highly reactive, and consequently, there is a rapid buildup of gel strength in the foaming reaction, which sometimes permits the foam to be obtained without use of a cell stabilizer. However, such unstabilized foams typically have very irregular and coarse cell structures, evidenced by surface voids. This problem has generally been addressed by using substituted certain polydimethylsiloxane-polyoxyalkylene or polyphenylmethylsiloxane-polyoxyalkylene copolymers as foam stabilizers.
Polysiloxane-polyoxyalkylene copolymer surfactants for use as stabilizers for high resilience polyurethane foam are disclosed, for example, in the following U.S. Pat. No. 3,741,917 of Morehouse; U.S. Pat. No. 4,478,957 of Klietsch et al.; U.S. Pat. No. 4,031,044 of Joslyn; U.S. Pat. No. 4,477,601 of Battice; U.S. Pat. No. 4,119,582 of Matsubara et al.; U.S. Pat. No. 4,139,503 of Kollmeier et al.; and several patents of Kilgour, U.S. Pat. Nos. 4,690,955; 4,746,683; and 4,769,174. These references variously disclose that the terminal oxygen atom of the polyoxyalkylene portion of the surfactant molecules may bear a hydrogen atom (Morehouse '917, Klietsch '957, Kollmeier '503), an alkyl group of 1-4 carbon atoms (Morehouse '917, Klietsch '957, Kilgour '955, '683, and '174), an alkyl group containing fewer than 10 atoms in total (Joslyn '044), an alkyl group containing a total of less than 11 carbon atoms (Battice '601), or a monovalent hydrocarbon group (Matsubara '582). Methyl capping is commonly used. In addition, several other capping groups are disclosed. Those skilled in the art apparently have not believed that there are any advantages to be gained by use of any particular alkyl capping groups.
Surfactants for stabilization of polyurethane foam are evaluated on the basis of several different performance characteristics. Primary among these is the potency or efficiency of the surfactant. The minimal amount of surfactant needed to provide good cell structure in the resulting foam is a relative measure of the potency. Polyurethane foam having good cell structure can be produced using less of a superior surfactant than would be required using a less potent surfactant. The ability to use less material is desirable in the foaming industry to lower the cost of foaming operations.
Of further concern in selecting a surfactant for polyurethane foam stabilization is the breathability or open-celled character of foam. High breathability (more open-celled character) of the foam is desirable, as it provides a greater processing latitude. A narrow processing latitude forces the foam manufacturer to adhere to very close tolerances in metering out the foaming ingredients, which cannot always be accomplished. Further, greater breathability provides foam that is considerably easier to crush, thus avoiding splits that might occur during crushing. This characteristic is particularly desirable in foamed parts that incorporate wire inserts, which are difficult to crush.
In the design and development of surfactants for use as stabilizers for high resilience polyurethane foam, there has traditionally been a trade-off between increasing the potency (efficiency) of the surfactant and lowering the breathability of the foam produced using it. It has generally been found that the more potent the surfactant, the lower the breathability of the foam made using it. In other words, the more potent surfactants generally afford poorer processing latitudes.
It would be very desirable to have silicone surfactants for stabilization of high resilience polyurethane foam, which afford both good potency and good breathability, thus providing foam manufacturers with relatively low surfactant costs as well as good processing latitude. Such surfactants are the subject of this application.